ABSTRACT
The apolipoprotein E gene (APOE) exists in three major alleles: APOE-ε2, APOE-ε3, and APOE-ε4. The frequency of these alleles in Caucasian populations is: APOE-ε2, 0.08; APOE-ε3, 0.78; APOE-ε4, 0.14 (Davignon et al., 1988; Ordovas et al., 1987). The apoE isoforms of these allelic variants have different arginine/cysteine compositions:
allele frequency isoform APOE-ε2: 0.08 apoE2 Cys 112 Cys 158 APOE-ε3 0.78 apoE3 Cys 112 Arg 158 + APOE-ε4 0.14 apoE4 Arg 112+ Arg 158+
Thus, the three isoforms differ in their charge (Zannis and Breslow, 1981) and in the presence of two, one, or zero cysteine residues.
